Myotomes  and Dermatomes
Published in the Times Standard
      Frequently a patient presents in my office with not only back or neck pain, but also with an area of numbness in an extremity or on the back or chest. This problem can usually be addressed through a few simple tests and corrected with Chiropractic.                                
      In my article on “Reflexes”, I mentioned the motor and sensory fibers of the spinal nerve in the reflex arc. Motor fibers innervate certain muscles, and sensory fibers innervate areas of the skin. The spinal nerve and its corresponding muscle is called a myotome while the skin area and its sensory spinal nerve is a dermatome. Each muscle in the body is innervated from a specific spinal cord/ and vertebral level. For example, the C5 cervical or neck vertebra level and its spinal nerve supplies nerve energy to the shoulder muscles and the biceps muscle that we use to bend our elbow.                                      
        Skin areas, innervated by the sensory portion of the spinal nerve, present patterns on the body that relate to specific spinal cord and vertebral levels. These dermatomes are named by the spinal nerve that supplies the energy, the exceptions being the jaw, face, and forehead to the top of the head. These areas are fed by three cranial nerves.                              
These patterns of dermatomes and the specific muscle groups are the same in most people. There can be some overlapping of the dermatomes.                                                           
        The specificity of  the vertebral level of spinal nerve relationship to the myotomes and dermatomes allows for another means of locating nerve impingement or spinal cord involvement. By testing muscles for weakness or skin areas for loss of sensation, one can narrow down the associated vertebral spinal nerve level. Further verification can be achieved by checking for tenderness over the spine or heat from inflammation, loss of or limited range of motion, and tightness or spasm of spinal muscles. Once the level or levels are located, the appropriate and necessary adjustment can be made to restore nerve flow. With the blockage or impingement released, the muscle, skin and nerve will return to normal function, through Chiropractic “naturally”.      
Crosbie Chiropractic
Michael H. Crosbie, D.C.
1828 Main Street
Fortuna, CA 95540
(707) 725-5668